#app {
  width: 100%;
  height: 100%;
  overflow: auto;
  overflow-x: hidden;
  position: relative;
}
#app .beijing {
  width: 100%;
}
#app .btn-box {
  position: absolute;
  width: 400px;
  height: 270px;
  top: 2280px;
  left: calc((100% - 400px) / 2);
  z-index: 2;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
}
#app .btn-box .btn {
  height: 120px;
}
